Polycystic ovary syndrome (PCOS) is a hyperandrogenic disorder that occurs in 5-10% of premenopausal women, often producing both infertiliy and increased risk of metabolic and cardiovascular disease. The combined evidence obtained by our core investigators strongly supports our central hypothesis that PCOS has a genetic basis linked to excess androgen production, and that the androgen excess programs the pathogenesis ofthe disorder. Common metabolic features of PCOS include obesity, insulin resistance, and hyperinsulinemia, and our studies in rodents and monkeys have revealed that prenatal androgen excess can program development of these metabolic PCOS symptoms. Since many of these same PCOS features develop in estrogen- or estrogen receptor alpha (ERa)-deficient rodents, and following ERa targeting in the hypothalamus, and since prenatal androgen exposure induces resistance to many hypothalamic acfions of estradiol (E2), we have proposed the novel hypothesis that androgenic programming of metabolic features of PCOS is mediated by induction of hypothalamic resistance to E2. However, the mechanisms by which E2 may act in the hypothalamus to regulate energy homeostasis, metabolism, adiposity, and body weight in women and non-human primates remains largely unknown, and the ability of androgens to program altered hypothalamic E2 responsiveness remains untested. We will therefore determine the effects of E2 on energy homeostasis, metabolism, and adiposity in ovariectomized marmosets. We will utilize ER-specific agonist treatments to determine which ER isoform mediates E2 effects on metabolism in this primate. In a second experiment we will use adeno-associated viral vectors to knock-down ERa in hypothalamic target nuclei to ascertain the importance of discrete neuronal ER populations in the regulation of body weight and metabolism by E2. Finally, we will determine whether prenatal and postnatal androgen excess induces metabolic features of PCOS in marmosets, and whether any such effects are mediated by induction of resistance to E2 actions.